1. Field of the Invention
The present invention relates to a power tool, such as a combustion-engined tool or an explosion-operated tool, formed in particular as a settling tool for driving in fastening elements and including a combustion chamber, a drive piston adjoining the combustion chamber and displaceable upon combustion of fuel in the combustion chamber, and an ignition device for igniting the fuel in the combustion chamber. The present invention also related to a method of cooling the combustion chamber of the power tool.
2. Description of the Prior Art
In power tools described above, fuel in form of fuel gas mixture or in a powder form, e.g., stored in a cartridge, is fed into the combustion chamber of a power tool. The ignition of the fuel with an ignition device provides for driving of a piston which is displaced in a cylinder associated with the combustion chamber. A fastening element, which was fed in the headpiece of the power tool, can be, thus, driven by the piston, e.g., in a wall.
Power tools, in particular, bolt settings tools in which the piston rearward movement is caused by cooling of residual gases and the resulting underpressure in the combustion chamber, are known. The temperature of the wall of the combustion chamber, which is usually a cylindrical wall, can reach, with a high setting frequently and high outer temperature, close to 150°. Thereby cooling of the residual gases in the combustion chamber and the speed of return movement are reduced or at least somewhat slows.
The return movement of the piston depends on a temperature difference between the residual gas and the temperature of the combustion chamber or cylindrical wall. The smaller is the temperature difference the slower the residual gas cools, and more time is required for return of the piston to its initial rearward position. This, in turn, reduces the setting frequency. For an effective, more rapid setting process a high cooling-down rate is required for a more rapid return of the piston to its initial position and, thus, for a high setting frequency. Moreover, with a more rapid return of the piston to its initial position, leakage become less relevant than with a slower return of the piston to its initial position.
Accordingly, an object of the present invention is a power tool that would provide a high setting rate with a longer running time and/or high environmental temperatures.
Another object of the present invention is a method that would provide for a high setting rate of a setting tool with its longer running time and/or high environmental temperatures.